Normal relationship between luminous threshold and critical flicker fusion frequency

Purpose: To establish the relation between differential luminous thresholds (DLT) and the critical flicker fusion frequency (CFF). Methods: Twenty-eight eyes of 28 healthy subjects, with previous perimetric experience, mean age 34.7 years (SD = 14.1) and a refractive error lower than 3 D (spherical equivalent), were examined twice using the Octopus 1-2-3 perimeter; once for measuring CFF with flicker perimetry (background 31.4 ash, stimulus Goldmann III at 4000 asb and I sec long), and the other with conventional DLT perimetry. TOP strategy and grid 32 were used in both cases. Results: A relationship of 1 dB = 1.27 +/- 0.03 Hz was obtained at the 74 points examined. The authors' previous estimation had some local variability, with average deviations of 1.25 Hz from the normal CFF values, the deviations being underestimated in the peripheral areas and mostly in the upper field. The relationship is more uniform in the present study. The deviation of the real local mean value from the estimated mean value is 0.6 Hz. The RAMS error value between the CFF and DLT on the 20-2 examined points was 7.9 Hz. The CFF age loss (0.075 Hz/year) was similar to DLT age loss (0.059 dB/year), with a ratio between them of 1.27. Conclusions: The authors found a tight functional dependence between DLT and CFF: I dB = 1.27 Hz, with the Octopus 1-2-3 and for the kind of stimulus used. This relationship between both physiological functions is more constant than has been previously reported, using different samples of subjects.